Simplify the following expression: $t = \dfrac{7}{9z} + \dfrac{-4}{9z}$
Explanation: Since the expressions have the same denominator we simply combine the numerators: $t = \dfrac{7 - 4}{9z}$ Combine like terms: $t = \dfrac{3}{9z}$ Simplify by dividing numerator and denominator by 3: $t = \dfrac{1}{3z}$